Brake lining wear warning system

ABSTRACT

A brake lining wear warning system for indicating when brake linings are dangerously worn and require replacement and provides a warning signal to a vehicle operator when the brake lining has worn a predetermined amount. Engagement of a detector with the brake drum initiates an operator warning signal.

United States Patent [191.

Lane et al.

May 22, 1973 BRAKE LINING WEAR WARNING SYSTEM Inventors: Buddy F. Lane;Donald E. Church,

both of Richmond, Ind.

Assignee: Avco Corporation, Richmond, Ind.

Filed: Aug. 12, 1971 Appl. No.: 171,071

US. Cl. ..340/52 A, ZOO/61.4 Int. Cl. ..B60t 17/22 Field of Search..340/52 R, 52 A, 52 B;

[56] References Cited UNITED STATES PATENTS 3,440,604 4/1969 Phillips..340/52 A 3,456,236 7/1969 Labartino et al. ..340/52 A PrimaryExaminerAlvin H. Wa ring Attorney-Charles M. Hogan and Eugene C. Goodale[5 7] ABSTRACT 8 Claims, 9 Drawing Figures lZ lO IZJ IO Uzi/IO T itfll3g TEE F3 Q3 4e 4e 4e 4e 44 44 '44 44 PATENIEW 3,735,343

sum 1 [1F 2 INVENTO DY F. LA ALD E.CHURCH BY W ATTORNEYS PATENTED 19753, 7 3 5 343 SHEET 2 [IF 2 F 58 LL INVENTORS BUDDY E LANE DONALD E.CHURCH ATTORNEkS &

BACKGROUND OF THE INVENTION This invention pertains to wear warningsystems and more particularly to a brake lining wear warning system forproviding the vehicle operator with a warning that the brake liningshave reached a point where continued use might be dangerous.

Vehicle brakes are not easily inspected to determine the amount of wearof the brake linings. Accordingly, it is not uncommon for vehicleoperators to continue driving a vehicle after the brake linings are wornto a dangerous condition. Continued use of such worn brake linings mayresult in scored brake drums which increases the danger of accidents,and also greatly increases the cost of repairs.

Many devices have been developed in the past to provide a signal to avehicle operator to inform him that brake lining wear has progressed apredetermined amount. However, these devices have generally beensophisticated, bulky and very expensive to manufacture and install invehicles. The operational reliability of these devices has been entirelyunsatisfactory and their anticipated widespread use has nevermaterialized. Many of the prior devices have utilized probes and thelike which protrude laterally through the brake linings.

A problem with this type probe is that it was often difficult to securethe probe within the brake lining material and, in addition, a portionof the brake lining is removed for the probe which decreases the amountof brake lining available for engagement with the brake drum.

Accordingly, it is an object of this invention to provide a brake liningwear warning system which is installed without decreasing the area ofthe brake lining engaging surface.

Another object of this invention is to provide a brake lining wearwarning system which is compact, easy to manufacture and install, andreasonably priced.

A still further object of this invention is to provide a brake liningwear warning system which does not require the brake structure to bedisassembled to determine if the linings are worn to. the point thatthey need replacing.

Yet another object of this invention is to provide a brake lining wearwarning system that does not interfere with normal operation of thebrake.

SUMMARY OF THE INVENTION This invention provides an improved brakelining wear warning system for indicating when brake linings have worn apredetermined amount and are in need of replacement. The warning systemincludes a wear detector which is attached to the brake shoe adjacentthe brake lining. The detector does not interfere with the brakelining-brake drum area of contact. The warning system will provide acontinuous danger signal even after the brakes have been disengaged ormay be so arranged as to provide a signal only when the brakes areapplied. The wear detector and warning system are of simple andeconomical construction, are efficient in operation and do not interferewith the normal braking action of the brake structure.

Other objects, details, uses and advantages of this invention willbecome apparent as the following description of the exemplaryembodiments thereof presented in the accompanying drawings proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings show presentexemplary embodiments of this invention in which:

FIG. 1 is an elevation view, partially in section, show ing the generallocation of the brake lining wear detector of this invention;

FIG. 2 is an enlarged elevational view of the wear detector illustratedin FIG. 1;

FIG. 3 is a sectional view taken along line 33 of FIG. 2;

FIG. 4 is a view taken along line 4-4 of FIG. 2;

FIG. 5 is a sectional view, similar to FIG. 3, illustrating anotherexemplary embodiment of the wear detector of this invention;

FIG. 6 is a view, similar to FIG. 4, illustrating the wear detector ofFIG. 5;

FIG. 7 is a schematic presentation of one form of the invention;

FIG. 8 is a schematic presentation of another form of the invention; and

FIG. 9 is a schematic presentation illustrating a third circuitembodying this invention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS Reference is now made toFIGS. 1 and 2 of the drawings, which illustrate one exemplary embodimentof the improved wear detector for use in a brake lining wear warningsystem, which is designated generally by the reference numeral 10. Thedetector 10 is mounted in a conventional brake structure. The brakestructure comprises a brake drum 12 having conventional brake shoes 14and 16 pivotally mounted therein. The brake shoes 14 and 16 arepivotally mounted on pin 18 and actuated by an hydraulic cylinder 20. Anautomatic adjuster 22 positions the shoes to assure engagement oflinings 24 and 26 with the interior surface 28 of the brake drum 12.

As shown in FIGS. 3 and 4, the wear detector 10 consists of two softmetallic conductive sheets or elements 30 and 32, such as copper, whichare bonded to a nonconductive sheet 34. The conductive elements 30 and32 are connected to the electrical motoring system, shown in FIG. 7, bymeans of the lead wires 36 and 38. The wear detector 10 is bondedto thebrake shoe 14 (FIGS. 1 and 2) by any suitable means. With prolonged use,the brake linings 24 and 26 will wear to a depth which is predeterminedand controlled by the thickness of the combined conductive elements 30and 32 and the non-conductive sheet 34. When the brake linings have wornto this predetermined thickness, the application of the brakes willcausethe brake drum 12 to complete the electrical circuit between theconductive elements 30 and 32. The completion of this circuit enables asuitable warning signal such as a lamp, indicating that brake liningreplacement is necessary.

Another exemplary embodiment of the wear detector of this invention isillustrated in FIGS. 5 and 6 of the drawings. The wear detector thusillustrated is very similar to the wear detector 10; therefore, suchwear detector will be designated generally by the reference numeral 10A.The main difference between wear detector 10A and the wear detector 10is in the construction of the electrical contacts. Two soft metallicstrips 40 and 42 are formed or crimped around the ends of lead wires 36Aand 38A. The metallic strips 40 and 42 may be made of anodized aluminumand bonded to the brake shoe 14A by any conventional means. The anodizedaluminum will provide a protective surface against various types ofunfavorable environments, as well as providing an insulator between thelead wires 36A and 38A and the brake shoe. When the brake lining 24A hasworn a sufficient amount, the brake drum will make contact between thestrips 40 and 42. When the brake drum wears through the anodizedsurface, the electrical circuit between the two strips 40 and 42 will becompleted so as to enable a suitable warning signal.

Referring now to FIG. 7, there is shown a schematic presentation of oneexemplary embodiment of a suitable circuit which may be used with thebrake lining wear warning system of this invention. It is seen that thesystem includes a plurality of wear detectors 10, one for each wheel.Each wear detector is connected with a reference point A by lead 38.Lead 36 is connected with an appropriate silicon controlled rectifier44. A suitable signal, such as a plurality of lamps 46,

one indicating each wheel, is connected to point A by leads 48 and toreference point B through SCR 44 and common lead 50. When the brakelining has worn a sufficient amount, the application of the vehiclebrakes causes one of the four brake drums 12 to contact the conductingelements of the wear detector 10. This action effectively shorts out thetwo exposed conductors on the brake shoe, thereby effecting a switchclosure. The closure of any one of the four wear detectors 10 appliesbattery power to the gate of the appropriate SCR 44. The application ofpower to the SCR will cause the SCR to go to the on state and enable theappropriate lamp 46. The utilization of this circuit provides that thelamp 46 will remain enabled even after the vehicle brakes have beendisengaged so that the brake drum 12 no longer contacts the weardetector 10. It should be noted that reference points A and B may beconnected for either positive ground or negative ground. In the positiveground condition, point A is considered as ground and point B is at anegative potential. In the negative ground condition, point A is at apositive potential and point B is at ground.

In FIG. 8, it is seen that the plurality of signal lamps have beenreplaced by a single indicating lamp 52. The wear detectors 10 from eachwheel are connected by a common lead 54 to an SCR 56. In thisembodiment, the lamp 52 will be enabled by the shorting out of any ofthe wear detectors 10. The potential of points A and B may likewise beconnected as hereinabove described.

FIG. 9 illustrates another embodiment of the warning system of thisinvention in which the signal lamp is only enabled when the brakes areapplied. In this embodiment, one side of the wear detectors 10 isconnected directly to a power source and the other side of the detector10 is connected directly with the signal lamp 58. Thus, the circuit toenable lamp 58 is only complete when the brake drum 12 is contacting thewear detector 10. Thus, the lamp 58 is only enabled at such times aswhen the brakes are applied.

It can be seen that the brake lining wear warning system of thisinvention provides a means to visually indicate to an operator when thebrake linings need replacement. The wear detector does not interferewith nor decrease the contact surface between the brake lining and brakedrum. Accordingly, the objectives hereinbefore set forth have beenaccomplished.

While present exemplary embodiments of this invention have beenillustrated and described, it will be recognized that this invention maybe otherwise variously embodied and practiced by those skilled in theart.

What is claimed is:

1. A brake lining wear warning system comprising in combination:

a brake drum;

a brake shoe selectively actuated to a brake applying position;

a brake lining mounted on a portion of the surface of said brake shoeand arranged to engage said brake drum in the brake applying position;

a lining wear detector mounted adjacent said lining on the portion ofsaid brake shoe surface not covered by said brake lining, said detectorhaving a predetermined thickness wherein said detector will engage saidbrake drum in the brake applying position after a predetermined amountof lining wear;

an electrical power source;

signal means electrically connected with said power source and said weardetector wherein contact of said wear detector with said brake drumenables said signal means to indicate that said lining has worn apredetermined amount.

2. The combination as set forth in claim 1 in which said wear detectorcomprises a first contact and a second contact, said contacts beingelectrically separated, said first contact being connected with thepower source and said second contact being connected with said signalmeans wherein engagement of said brake drum with said first and secondcontacts provides electrical continuity therebetween to enable saidsignal means.

3. The combination as set forth in claim 2 in which said first andsecond contacts comprise soft metallic elements of a predeterminedthickness, said elements being mounted on a non-conductive strip, and inwhich non-conductive strip is secured to said brake shoe on the portionof said brake shoe surface not covered by said brake lining.

4. The combination according to claim 2 in which said first and secondcontacts are metallic strips of anodized aluminum to electricallyisolate one strip from the other and each strip from said brake shoe andin which said strips are secured directly to said brake shoe.

5. The combination as set forth in claim 1 in which said signal means isa lamp and further comprising a silicon controlled rectifierelectrically connected between said lamp and said wear detector, saidsilicon controlled rectifier normally being in a non-conducting stateand being switched to the conducting state in response to said brakedrum engaging said wear detector wherein said lamp is enabled by theswitching of said silicon controlled rectifier to the conducting state.

6. The combination as set forth in claim 5 in which an wear detector isassociated with each wheel of a vehicle, and in which a separate lampand control means is associated with each wear detector wherein one lampindicates the condition of the brake lining for a given wheel.

7. The combination as set forth in claim 5 in which an wear detector isassociated with each wheel of a vehicle, said wear detectors beingelectrically connected to a common lamp and control means wherein saidlamp is enabled by any one of said wear detectors.

8. The combination as set forth in claim 1 in which said wear detectoris mounted substantially on the upper surface of said brake shoe.

1. A brake lining wear warning system comprising in combination: a brakedrum; a brake shoe selectively actuated to a brake applying position; abrake lining mounted on a portion of the surface of said brake shoe andarranged to engage said brake drum in the brake applying position; alining wear detector mounted adjacent said lining on the portion of saidbrake shoe surface not covered by said brake lining, said detectorhaving a predetermined thickness wherein said detector will engage saidbrake drum in the brake applying position after a predetermined amountof lining wear; an electrical power source; signal means electricallyconnected with said power source and said wear detector wherein contactof said wear detector with said brake drum enables said signal means toindicate that said lining has worn a predetermined amount.
 2. Thecombination as set forth in claim 1 in which said wear detectorcomprises a first contact and a second contact, said contacts beingelectrically separated, said first contact being conNected with thepower source and said second contact being connected with said signalmeans wherein engagement of said brake drum with said first and secondcontacts provides electrical continuity therebetween to enable saidsignal means.
 3. The combination as set forth in claim 2 in which saidfirst and second contacts comprise soft metallic elements of apredetermined thickness, said elements being mounted on a non-conductivestrip, and in which non-conductive strip is secured to said brake shoeon the portion of said brake shoe surface not covered by said brakelining.
 4. The combination according to claim 2 in which said first andsecond contacts are metallic strips of anodized aluminum to electricallyisolate one strip from the other and each strip from said brake shoe andin which said strips are secured directly to said brake shoe.
 5. Thecombination as set forth in claim 1 in which said signal means is a lampand further comprising a silicon controlled rectifier electricallyconnected between said lamp and said wear detector, said siliconcontrolled rectifier normally being in a non-conducting state and beingswitched to the conducting state in response to said brake drum engagingsaid wear detector wherein said lamp is enabled by the switching of saidsilicon controlled rectifier to the conducting state.
 6. The combinationas set forth in claim 5 in which an wear detector is associated witheach wheel of a vehicle, and in which a separate lamp and control meansis associated with each wear detector wherein one lamp indicates thecondition of the brake lining for a given wheel.
 7. The combination asset forth in claim 5 in which an wear detector is associated with eachwheel of a vehicle, said wear detectors being electrically connected toa common lamp and control means wherein said lamp is enabled by any oneof said wear detectors.
 8. The combination as set forth in claim 1 inwhich said wear detector is mounted substantially on the upper surfaceof said brake shoe.